Infrared Temperature Challenges – Environmental Interference
In our previous installments of this series, we discussed the challenges of measuring IR temperature through a window and the complications introduced by low-emissivity (shiny) surfaces. In this article, we’ll tackle another common issue: environmental interference. Whether it’s dust, steam, smoke, or other particulates in the environment, these can all have a profound impact on your infrared temperature measurements.
How Particulates Affect IR Measurements
When you measure temperature with an infrared (IR) sensor, you’re capturing the infrared radiation emitted by the target. However, if there’s a cloud of dust, steam, smoke, or even fog between the sensor and the target, that path can become obstructed or scattered:
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Absorption: Certain gases or water vapor may absorb IR radiation before it reaches your sensor. This leads to artificially low readings.
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Scattering: Fine particles like dust or smoke can scatter IR energy in random directions, causing less radiation to make it to the sensor.
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Attenuation: Combined absorption and scattering results in reduced intensity of the IR signal. This often manifests as unstable or inaccurate temperature measurements.
Essentially, whenever something sits between your sensor and the surface you’re trying to measure, there’s a risk that your readings will be skewed or inconsistent.
Common Sources of Interference
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Dust
In industrial environments such as foundries, grain silos, and cement plants, dust can be constantly circulating. When dust settles on or passes through the optical path of your IR sensor, it can block or scatter the emitted radiation. -
Steam & Fog
Facilities like food processing plants, breweries, or chemical factories often have high humidity or steam-filled areas. Steam is particularly problematic because it doesn’t just scatter IR radiation—it can also absorb certain infrared wavelengths. -
Smoke
In high-temperature processes, such as combustion or furnace applications, smoke is a frequent byproduct. Dense smoke can significantly attenuate IR signals and lead to wide fluctuations in measured temperatures.
Mitigating Environmental Interference
1. Proper Sensor Placement
Whenever possible, position your IR sensor to minimize exposure to the worst of the dust or steam. Even slight repositioning to a less turbulent area can reduce interference.
2. Air Purge Systems
An air purge involves blowing clean, dry air (or inert gas) across the sensor lens or the viewing window. This constant flow helps keep dust or condensation from collecting on the optics. Many IR sensors have optional air purge collars or protective hoods available.
3. Fiber Optic Pyrometers
In especially harsh environments, fiber optic pyrometers can be a good choice. With these devices, the optical head is separated from the main electronics by a fiber cable. This allows the detector and processing electronics to remain in a cleaner, cooler area, while only the small optical head is exposed to the harsh environment.
4. Protective Enclosures
Enclosures with built-in windows or ports can also help protect the sensor from dust and moisture. Use a suitable window material (as discussed in our first article) if your enclosure needs to remain sealed.
5. Regular Maintenance & Cleaning
Even with air purge systems and enclosures, some cleaning is inevitable. Regularly inspecting and cleaning the sensor lens or window goes a long way toward ensuring consistent readings.
How to Choose the Right IR Sensor
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Check the Spectral Range
Different IR sensors operate at different wavelengths. If steam or other vapors are your primary concern, certain wavelengths may be less affected by water vapor absorption. Always review the sensor’s spectral response in relation to your environment. -
Select Durable Housings
Look for sensors rated for use in dusty or wet conditions (IP ratings). This ensures the housing itself is less likely to allow dust or moisture inside. -
Consider Your Process Temperature
High-temperature processes combined with environmental interference may require specialized sensors. For instance, many of IOThrifty’s infrared sensors are offered with various measurement ranges and housings to handle different environmental conditions. -
Evaluate Mounting and Access
Ensure that the sensor’s maintenance (such as cleaning or repositioning) can be performed easily and safely. If your environment is extremely hot, toxic, or otherwise inaccessible, fiber optic solutions or remote monitoring options might be ideal.
Example Applications
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Cement & Lime Kilns: Dust-laden environments where fiber optic pyrometers and air purge systems are critical to accurate readings.
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Food & Beverage Processing: Steam and condensation often reduce measurement reliability; carefully positioned sensors with periodic cleaning are essential.
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Metal Casting & Foundries: Smoke and fumes can disrupt IR temperature measurements, making robust housings and purge systems particularly useful.
Conclusion
Environmental interference from dust, steam, smoke, or other particulates is a common issue in many industrial processes. However, with the right choice of sensor, accessories (like air purge systems), and careful placement, you can mitigate these challenges to achieve accurate, repeatable temperature measurements.
If you have any questions or need assistance selecting the best infrared sensor for your application, reach out to IOThrifty’s team of experts at service@iothrifty.com. We carry a wide range of IR sensors and accessories designed to handle harsh industrial environments. Let us help you find the perfect solution.